If condition in script

[#1]

please advise on how to create a If condition in script for below criteria

for the given field A ,Field B, field C

if  filter=1 and (respective Field A and Field B) irrespective of field C  length is 0 or >0 it should be '1'

if filter =0 and (respective Field A and Field B) irrespective of field C length is 0 or >0 it should be '0'

thanks.

[sunny_talwar]

What exactly is filter? Is that a field from database as well? Can you share some sample data with expected output?